Elephant Circulatory System
Because of the size of the elephant’s body, the heart has to be strong, sizeable and efficient to ensure that blood reaches every extremity at a suitable blood pressure. The blood travelling this distance also has to have sufficient oxygen to enrich all of the tissue in the elephant’s body. For this reason, the elephant’s haemoglobin has an increased affinity for oxygen compared to other mammals. This eases the amount of work that the heart needs to do as the blood being carried to the organs and tissues is much richer in oxygen. The heart produces a strong, prolonged beat or pump approximately 28 times each minute. In comparison, the human heart beats an average of 70 times a minute.
Elephants have a higher blood pressure than humans do. This is because their blood vessels are longer and wider, with some reaching an amazing 3.5 metres in length. To keep these veins and arteries from collapsing due to their size, the pressure of the blood inside needs to be higher. Arteries (the vessels that carry blood away from the heart) are also aided by the fact that they are supported by elastic fibres made up of muscle cells. Likewise, veins (vessels that carry blood from the rest of the body back to the heart) have thicker walls supporting them.
Two curious differences from other mammals are notable with respect to the circulatory system of the elephant. Firstly, the ventricles within the heart are separated at their apex. The ventricle is the larger of the two types of heart chambers (the smaller one being the atrium) and is responsible for pumping blood out of the heart. Secondly, the venae cavae (the veins carrying blood from the lower half of the body into the right atrium) are paired rather than singular.